Information embedding apparatus and information embedding method for adding information to document image by embedding information therein, information detecting apparatus and information detecting method

ABSTRACT

In an information embedding apparatus, an image compositing portion selectively reads an embedding pattern from a plurality of types of the embedding patterns in accordance with an embedding information for a background of a document image. The image compositing portion further composites the read embedding pattern into the background of the document image in a document image data generated based on a document data and outputs the composite document image data. The embedding pattern includes a data dot placed at a position in accordance with the embedding information, a position dot placed at a position for instructing a reference position used for identifying the position of the data dot, and an assisting dot placed at a position for assisting the instruction of the reference position by the position dot.

This application is a divisional application of application Ser. No.11/435,097, filed May 16, 2006, which is based on Japanese PatentApplication No. 2005-145806 filed with the Japan Patent Office on May18, 2005, the entire content of which is hereby incorporated byreference.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an information embedding apparatus, aninformation embedding method, an information detecting apparatus and aninformation detecting method, more particularly to an informationembedding apparatus and an information embedding method for adding aninformation to a document image by embedding the information therein,and an information detecting apparatus and an information detectingmethod for detecting the information embedded in and added to thedocument image from the printed document image.

2. Description of the Related Art

An electronic watermarking technology in which dots are printed in adocumented image so that data is embedded therein has been proposed. Forexample, as recited in Japanese Laid-Open Patent Publication No.2004-128845, the dots to be embedded in the document image as theelectronic watermark are embedded in accordance with three differentarrangement methods so that each of the embedding arrangement methods(types) has a meaning. Further, as recited in Japanese Laid-Open PatentPublication No. 2003-101762, the data is embedded in the document imagedepending on in which direction the dot is darker or lighter.

The technology of “electronic watermarking for document” for embeddingdata in a background of the document image as a ground pattern can alsobe applied to MFP (Multi Function Peripherals)/LBP (Laser Beam Printer).A method for embedding and detecting the data in such a manner that aresistance against a noise factor (any unnecessary dot unintentionallyprinted, dot resulting from a screening process and the like) can beassured was necessary in scanning the printed document in which the datais embedded as the ground pattern by a scanner so that the data isdetected. Further, it was necessary that simplified processing stepswhich can be realized in terms of hardware constitute the detectingfunction in order to install the detecting function in the MFP.

However, the method recited in Japanese Laid-Open Patent Publication No.2004-128845 is not practical in use because it fails to attain anexpected resistance against the noise factor. Further, it is notpossible to add such a dot that can constitute the background image ofthe document image because each of the different dot arrangementsincludes the meaning of the data.

In the method recited in Japanese Laid-Open Patent Publication No.2003-101762, the data is embedded depending on in which direction thedot is darker or lighter in the document image, which demands acomplicated processing when the embedded data is detected. Therefore, itis difficult to make the method into hardware. Further, the method failsto achieve a high-speed processing as software either since a detectingapparatus undergoes too large a load.

SUMMARY OF THE INVENTION

Therefore, a main object of the present invention is to provide aninformation embedding apparatus, an information embedding method, aninformation detecting apparatus and an information detecting methodcapable of assuring a resistance against a noise factor.

Another main object of the present invention is to provide aninformation embedding apparatus, an information embedding method, aninformation detecting apparatus and an information detecting methodcapable of realizing processing steps which can be realizedhardware-wise.

In order to achieve the foregoing objects, an information embeddingapparatus according to an aspect of the present invention includes anembedding pattern storing portion for storing a plurality of types ofembedding dot patterns, an embedding pattern reading portion for readingthe embedding dot pattern indicating an information to be embedded in abackground of a document image from the embedding pattern storingportion, and an embedding compositing portion. The embedding compositingportion composites the embedding dot pattern read by the embeddingpattern reading portion with the background of the document image in adocument image data generated based on a document data, and outputs thedocument image data composited with the embedding dot pattern. Theembedding dot pattern includes a data dot placed at a position inaccordance with the information to be embedded, a position dot placed ata position for instructing a reference position used for identifying theposition of the data dot, and an assisting dot placed at a position forassisting the instruction of the reference position by the position dot.

According to the present invention, the embedding dot pattern includessuch a plurality of dots as the position dot placed at the position forinstructing the reference position used for identifying the position ofthe data dot and the assisting dot placed at the position for assistingthe instruction of the reference position by the position dot inaddition to the data dot placed at the position in accordance with theinformation to be embedded. Therefore, the position dot and theassisting dot can be used to detect the data dot. Accordingly, the datadot can be easily identified from a positional relationship between theplurality of dots even if the background of the document image includessuch a noise factor as any unnecessary dot unintentionally printed ordot resulting from a screening process. Further, a plurality of types ofthe embedding dot patterns are stored in the embedding pattern storingportion. According to the present invention, the embedding dot patternindicating the information to be embedded is read from the embeddingpattern storing portion, and the read embedding dot pattern is simplycomposited with the background of the document image. Therefore, anycomplicated processing is unnecessary, and it is easy to constitute afunction relating to the compositing process and an apparatus having thefunction as hardware.

The information embedding apparatus according to the present inventionpreferably further includes an additional pattern storing portion forstoring a plurality of types of additional dot patterns indicating dotpatterns different from the embedding dot patterns, an additionalpattern reading portion for reading the additional dot patternindicating the information to be added to the background of the documentimage from the additional pattern storing portion, and an additioncompositing portion. The addition compositing portion composites theadditional dot pattern read by the additional pattern reading portionwith the background of the document image in the document image datagenerated based on the document data. The addition compositing portionthereafter outputs the document image data composited with theadditional dot pattern.

Therefore, the embedding dot pattern indicating the information to beembedded and the additional dot pattern indicating the additionalinformation are composited into the background, however, these two dotpatterns are different from each other. Therefore, even after thebackground, the embedding dot pattern and the additional dot pattern arecomposited with one another, the embedding dot pattern can be detectedfrom the composite document image data.

The different embedding dot patterns corresponding to a respectiveplurality of different values are preferably stored in the embeddingpattern storing portion. The embedding pattern reading portion includesan embedding data forming portion for converting the information to beembedded into a bit sequence indicating the information. The embeddingpattern reading portion reads the embedding dot pattern corresponding toa value of each bit in the bit sequence converted by the embedding dataforming portion from the embedding pattern storing portion.

Therefore, the compositing process in which the plurality of differenttypes of the embedding dot patterns are selected and used depending onthe contents instructed by the information to be embedded, that is thearrangements of the values of the bit sequence, can be realized.

As a preferable mode of the foregoing constitution, the differentadditional patterns corresponding to the plurality of different valuesare stored in the additional pattern storing portion. The additionalpattern reading portion reads the information to be added as an elementvalue and reads the additional dot pattern corresponding to the readelement value from the additional pattern storing portion.

Therefore, the plurality of additional dot patterns can be selected andcomposited in accordance with the contents instructed by the informationto be added.

As a preferable mode of the foregoing constitution, a dot density isdifferent in each of a plurality of types of the additional dotpatterns. Therefore, the background into which the additional dotpattern is composited can present a gradation of the pattern.

As a preferable mode of the foregoing constitution, the additional dotpattern includes an independent dot. Assuming that the document imagedata into which the additional dot pattern is composited is printed, andthe printed document is copied by a copying machine, the independent dotis erased on the image constituting the copying result because thecopying machine has such a function that presents the background as awhite background. Therefore, whether or not the document image wascopied or not (including illegal copy) can be determined in one glancebecause the additional dot pattern cannot maintain its original patternin the background of the copied document image.

The independent dot is erased, and the additional dot pattern in thebackground thereby changes into an insignificant rough pattern, as aresult of which it becomes more difficult to discriminate the embeddingdot pattern in the background of the copied document image. Therefore,the information to be embedded can effectively remain confidential inthe background.

As a preferable mode of the foregoing constitution, an additioncompositing portion is further provided. The addition compositingportion composites the additional dot pattern indicating the dot patterndifferent from the embedding dot pattern with the background of thedocument image in the document image data generated based on thedocument data, and outputs the document image data composited with theadditional dot pattern. The addition compositing portion compares athreshold value previously set in each element in a threshold patternpresented by a two-dimensional element matrix having a same size as thatof the background of the document image to a corresponding element valuein the background. Then, the addition compositing portion outputs thecorresponding element value to the composite document image data inaccordance with a result of the comparison.

Therefore, the preparation of one threshold pattern allows thecompositing process in which the plurality of additional dot patternsare used. As a result, a memory capacity relating to the additionstoring portion for storing the plurality of additional dot patterns canbe saved.

An information detecting apparatus for detecting a predeterminedinformation in accordance with a predetermined dot pattern printed on apredetermined region of a sheet of paper according to another aspect ofthe present invention includes a particular element dot detectingportion and an information detecting portion. The particular element dotdetecting portion scans the predetermined region using an element matrixfor detecting an element corresponding to an identifying dot used foridentifying the predetermined information of the predetermined dotpattern and detects a dot of an element in the predetermined regionrelevant to the particular element corresponding to the identifying dotof the element matrix. The information detecting portion detects thepredetermined information based on a result of the detection by theparticular element dot detecting portion and the predetermined dotpattern.

Thus, the predetermined region is scanned by means of the element matrixso that the predetermined information is detected. In the scan, the dotsrelevant to all of the elements of the element matrix are not detected,but the dot is limitedly detected for a part of the elements in thepredetermined region relevant to the particular element corresponding tothe identifying dot. Therefore, the scan using the element matrix, whichis not a complicated processing, can be easily realized in terms ofhardware. Further, when the process is realized in terms of software inorder to detect the dot of the limited partial element, the informationcan be speedily detected.

Further, even if any dot which does not follow the dot pattern, forexample, an additional dot (including smear generated when printed andnoise component) is printed on the paper, the detection can avoid anyerror resulting from the additional dot because the dot of the elementis detected in accordance with the dot arrangement of the dot pattern.

As a preferable mode of the foregoing constitution, the dot patternincludes a data dot placed at a position in accordance with informationto be embedded, a position dot placed at a position for instructing areference position used for identifying the position of the data dot,and an assisting dot placed at a position for assisting the instructionof the reference position by the position dot. The identifying dot is adot for detecting the position of the data dot.

Therefore, even if such a noise factor as any unnecessary dotunintentionally printed or dot printed in the screening process ispresent in the predetermined region, a relative positional relationshipindicated by the plurality of dots, which are the data dot, position dotand assisting dot, allows the data dot placed at the position inaccordance with the predetermined information to be easily identified.

The identifying dot preferably denotes the data dot. The identifying dotpreferably denotes the position dot.

The particular element dot detecting portion preferably detects the dotof the element in the predetermined region corresponding to the elementof the element matrix relevant to a position where the dot is not placedin the predetermined dot pattern. Then, the particular element dotdetecting portion detects the dot of the element in the predeterminedregion corresponding to the particular element of the identifying dot inthe element matrix based on a result of the detection. A part of theelements includes the element of the element matrix relevant to theposition where the dot is not placed in the dot pattern.

Therefore, the element of the element matrix relevant to the positionwhere the dot is not placed in the predetermined dot pattern is alsoreferenced for the detection, the dot pattern whose conditions includethe absence of the dot can be applied. As a result, the noise (dotunintentionally printed) can be effectively eliminated in the detection.

According to the aspect of the present invention, even if the noise suchas the unnecessary dot unintentionally printed or the dot resulting fromthe screening process is included in the background of the documentimage, the positional relationship between the plurality of dots allowsthe data dot to be easily identified.

Further, according to the present invention, a plurality of types of theembedding dot patterns are previously stored in the embedding patternstoring portion, and the embedding dot pattern indicating theinformation to be embedded is read from the embedding pattern storingportion, and the read embedding dot pattern is composited with thebackground of the document image. This processing is not complicated andcan be easily realized hardware-wise.

According to the another aspect of the present invention, the scan usingthe element matrix is executed in order to detect the predeterminedinformation. In the scan, the dots relevant to all of the elements inthe element matrix are not detected, but the dot is limitedly detectedfor the partial element in the predetermined region relevant to theparticular element corresponding to the identifying dot. The processingrelating to the scanning, which is not complicated, can be easily madeinto hardware. Further, the speedy information detection can be obtainedbecause the dot of the partial element is limitedly detected.

Further, even if any dot which does not follow the dot pattern, forexample, the additional dot (including smear generated when printed andnoise component) is present, the detection can avoid any error resultingfrom the other additional dot because the dot of the element is detectedin accordance with the dot arrangement of the dot pattern.

The foregoing and other objects, features, aspects and advantages of thepresent invention will become more apparent from the following detaileddescription of the present invention when taken in conjunction with theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows an example of functional components of an informationembedding apparatus.

FIG. 2 shows a configuration of a computer in which informationembedding apparatuses and an information detecting apparatuses accordingto respective preferred embodiments of the present invention areinstalled.

FIG. 3 shows an example of a printed document.

FIGS. 4A and 4B each shows an example of an embedding pattern.

FIG. 5 shows an exemplified arrangement of data cells with respect to animage of a document image data.

FIG. 6 shows a state where dots are embedded in accordance with thearrangement shown in FIG. 5.

FIG. 7 is a flow chart of an example of processing steps by an imagecompositing portion.

FIG. 8 shows another exemplified arrangement of data cells with respectto the image of the document image data.

FIG. 9 is a descriptive view of a role of a position representationassisting dot.

FIG. 10 is a descriptive view of the role of the position representationassisting dot.

FIG. 11 is a descriptive view of the role of the position representationassisting dot.

FIG. 12 shows an example of an additional information.

FIG. 13 shows an example of a printed document in which the additionalinformation has been embedded.

FIGS. 14A-14D each shows an example of an additional pattern.

FIG. 15 shows an exemplified arrangement of the additional informationwith respect to the image of the document image data.

FIG. 16 shows an example of a composite image data in which theadditional information has been embedded.

FIG. 17 is a flow chart of an example of processing steps by abackground adding portion.

FIG. 18 shows an example of a threshold pattern.

FIG. 19 is a flow chart of another example of the processing steps bythe background adding portion.

FIG. 20 is a flow chart of still another example of the processing stepsby the background adding portion.

FIGS. 21A-21F each shows another example of the additional pattern.

FIGS. 22A and 22B each shows another example of the embedding pattern.

FIGS. 23A-23D each shows still another example of the embedding pattern.

FIGS. 24A and 24B each shows still another example of the embeddingpattern.

FIG. 25 shows an example of a detecting pattern of a positionrepresenting dot.

FIGS. 26A and 26B each shows still another example of the embeddingpattern.

FIG. 27 shows another example of the detecting pattern of the positionrepresenting dot.

FIG. 28 shows another example of the functional components of theinformation embedding apparatus.

FIGS. 29A-29H each shows still another example of the additionalpattern.

FIG. 30 is a flow chart of another example of the processing steps bythe image compositing portion.

FIG. 31 shows an exemplified pattern arrangement based on an embeddinginformation and the additional information with respect to the documentimage.

FIG. 32 shows a state where the information is embedded in accordancewith FIG. 31.

FIG. 33 shows an example of functional components of an informationdetecting apparatus.

FIG. 34 shows an example of a position filter.

FIG. 35 shows an example of a filtering processing result obtained bythe position filter.

FIG. 36 shows an example of a multi-value image data as a scanningresult.

FIG. 37 shows an example of a filtering processing result of the imageshown in FIG. 36.

FIG. 38 shows an example of a data filter.

FIG. 39 shows an example of a filtering processing result obtained bythe data filter.

FIG. 40 shows an exemplified image resulting from the filteringprocessing.

FIG. 41 is a flow chart of entire processing steps of the filteringprocessing.

FIG. 42 is a flow chart of processing steps by a position representingdot extracting portion.

FIG. 43 is a flow chart of processing steps by a data representing dotextracting portion.

FIG. 44 shows another example of the position filter.

FIG. 45 shows still another example of the position filter.

FIG. 46 shows still another example of the position filter.

FIG. 47 shows an image having a noise resulting from the scan.

FIG. 48 shows an example of a filtering processing result including awrong dot.

FIG. 49 shows an example of a filtering processing result not includingthe wrong dot.

FIG. 50 shows an example of a data filter for a data 0.

FIG. 51 shows an example of a data filter for a data 1.

FIG. 52 shows a tilted multi-value image data resulting from the scan.

FIG. 53 shows still another example of the position filter.

FIG. 54 shows a filtering result of the tilted multi-value image dataresulting from the scan.

FIG. 55 shows an exemplified arrangement of the embedding informationand the additional information.

FIG. 56 shows a state where the informations are embedded in accordancewith the arrangement shown in FIG. 55.

FIG. 57 shows another example of the data filter for the data 0.

FIG. 58 shows another example of the data filter for the data 1.

FIG. 59 shows an example of extraction of the data 0 resulting from thefiltering processing.

FIG. 60 shows an example of extraction of the data 1 including the wrongdot resulting from the filtering processing.

FIG. 61 shows another example of the extraction of the data 0 resultingfrom the filtering processing.

FIG. 62 shows another example of the extraction of the data 1 resultingfrom the filtering processing.

FIG. 63 shows a configuration of a personal computer in which theinformation embedding apparatuses and the information detectingapparatuses according to the preferred embodiments are installed.

FIG. 64 shows a configuration of an MFP in which the informationembedding apparatuses and the information detecting apparatusesaccording to the preferred embodiments are installed.

FIG. 65 shows the configuration of the personal computer in which theinformation embedding apparatuses and the information detectingapparatuses according to the preferred embodiments are installedtogether with input and output data.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, preferred embodiments of the present invention aredescribed referring to the drawings. In this specification, aninformation embedding apparatus for embedding (compositing) aconfidential information and the like in a background of an image as aso-called electronic watermark is described in preferred embodiments1-6, and an information detecting apparatus for detecting theinformation for the electronic watermark thus embedded is described inpreferred embodiments 7-11.

An example of functional components of the information embeddingapparatus is shown in FIG. 1. A configuration of a computer in which theinformation embedding apparatuses and the information detectingapparatuses according to the preferred embodiments are installed isshown in FIG. 2.

Referring to FIG. 2, a computer 60 in which the information embeddingapparatus and the information detecting apparatus are installed includesa MPU (Micro Processing Unit) 61 for intensively controlling thecomputer itself, a memory 62 in which various informations, programs orthe like are stored, a HDD (Hard Disk Drive) 63, an FDD (FD Driver) 64to which an FD (Flexible Disk) 65 is detachably attached for accessingattached FD 65, and a DVD driver 66 to which a DVD (Digital VersatileDisc) 67 is detachably attached for accessing attached DVD 67. Computer60 further includes a keyboard 68 for inputting the various informationsfrom outside, and a scanner 70 connected via an I/F (abbreviation forinterface) 69. To computer 60 are connected a display portion 71 foroutputting the various informations and a printer 73 controlled by aprinter driver 72. Computer 60 further includes external variouscommunication lines (including Internet) 75 and a communication I/F 74for transmitting and receiving the informations with respect to computer60.

Processing steps for embedding the information and processing steps fordetecting the information according to the respective preferredembodiments, which will be described later, are previously stored inmemory 62, HDD 63, FD 65, DVD 67 and the like as programs. MPU 61 readsthe programs from these recording media and executes the read programsso that the processing steps for embedding the information and theprocessing steps for detecting the information are implemented. Computer60 shown in FIG. 2 can communicate with outside via communication lines75. Therefore, the programs may be downloaded into the recording mediafrom outside via communication lines 75.

FIG. 1 shows functional components of an information embedding apparatus10. In information embedding apparatus 10, a document data 11 of adocument image in which the information is embedded, an embeddinginformation 12 corresponding to the confidential information for theelectronic watermark to be embedded in the background of the documentimage, an additional information 13 to be added to the background of thedocument image, a plurality of embedding patterns 14 to be embedded inthe document image, and a plurality of additional patterns 15 andthreshold pattern 16 to be added to the background of the document imageare stored in predetermined memory regions such as memory 62, HDD 63,DVD 67, FD 65 and the like. Information embedding apparatus 10 includesa document image forming portion 17, an embedding data forming portion18, an image compositing portion 20, an output processing portion 21 anda background adding portion 23 (or a background adding portion 231).These portions are previously stored as programs in the predeterminedmemory regions such as memory 62, HDD 63, DVD 67, FD 65 and the like.These programs are read from the predetermined memory regions by MPU 61and executed, so that the functions of the respective portions arerealized. Background adding portions 23 and 231 are not simultaneouslyactivated, and one of them is selectively activated.

In an operation, document image forming portion 17 reads document 11 andgenerates an image data 24 showing an image in a state document data 11is printed on a sheet of paper per page based on read document data 11.Document image data 24 is a black and white two-value image. On theimage, white elements (elements whose values are 0) constitute thebackground, while black elements (elements whose values are 1)constitute a character region (region where ink is printed). Therefore,the image and the background are discriminated from each other based onthe criteria.

Document image forming portion 17 outputs document image data 24.Embedding data forming portion 18 reads embedding information 12, andforms and outputs an embedding data 25 based on read embeddinginformation 12. In the processing of embedding data forming portion 18,first, embedding information 12 is converted into an N-value code, andconverted embedding information 12 is outputted as embedding data 25. Nis an arbitrary value, and N=2 in this specification. Therefore, thegenerated code of embedding data 25 is a two-value code and expressed ina bit sequence of 0 and 1.

Image compositing portion 20 inputs document image data 24 supplied fromdocument image forming portion 17 and embedding data 25 supplied fromembedding data forming portion 18, and embeds the information indocument image data 24 in accordance with embedding data 25. Imagecompositing portion 20 selectively supplies a composite image data 27obtained as a result of the information embedding to one of outputprocessing portion 21 and background adding portion 23 based on asupplied selection instruction 29. More specifically, composite imagedata 27 is outputted to background adding portion 23 in the case ofembedding the information such as image in the background of thecomposite image, while being outputted to output processing portion 21otherwise. It is assumed that selection instruction 29 is supplied fromoutside when a user operates keyboard 68.

Output processing portion 21 inputs composite image data 27 suppliedfrom image compositing portion 20 or a composite image data 28 includingthe background supplied from background adding portion 23, and printsout an image in accordance with the inputted image data. As a result, aprinted document (paper) 22 is obtained.

Background adding portion 23 (or background adding portion 231) reads anadditional information 13 when composite image data 27 is suppliedthereto, and reads an additional pattern 15 indicated by read additionalinformation 13. Additional information 13 shows a type of an image data.Background adding portion 23 reads additional pattern 15 in accordancewith a value of each element in the image data shown by additionalinformation 13.

Background adding portion 23 (or background adding portion 231) inputscomposite image data 27 outputted from image compositing portion 20 andadds additional pattern 15 based on additional information 13 to thebackground of inputted composite image data 27. As a result, compositeimage data 28 including the background is thereby outputted to outputprocessing portion 21. Therefore, the document image resulting fromcomposite image data 28 including the background is obtained as printeddocument (paper) 22 via output processing portion 21.

Background adding portions 23 and 231 do not simultaneously function.One of the portions starts its operation in response to selectioninstruction 230, while the other is remains non-operable. Selectioninstruction 230 is supplied from outside by the user via keyboard 68.

Preferred Embodiment 1

In a preferred embodiment 1 of the present invention, informationcharacterized in having a dot for representing a position, a dotassisting the representation of the position and a dot for representingthe embedding data is embedded by image compositing portion 20.Referring to FIG. 1, image compositing portion 20 embeds data ofembedding information 12 as a dot pattern in the background of the imageof inputted document image data 24. An example of printed document 22resulting from the embedding is shown in FIG. 3. In FIG. 3, the data ofembedding information 12 is embedded in the document image so that thedata cannot be easily visually recognized.

In FIG. 1, a plurality of different embedding patterns 14 are stored inthe memory in association with each possible value of each bit in thebit sequence of embedding data 25 for each of the values. In a similarmanner, plurality of different additional patterns 15 are stored in thememory in association with each possible value of each element of theimage data shown by additional information 13 for each of the values.

Image compositing portion 20 selectively reads embedding pattern 14shown in FIG. 4A when the value is 0 (referred to as data 0) andselectively reads embedding pattern 14 shown in FIG. 4B when the valueis 1 (referred to as data 1) for each bit of the bit sequence ofembedding data 25. Then, image compositing portion 20 composites thebackground image and read embedding pattern 14 into each other in such amanner that read embedding pattern 14 is embedded in the background ofthe image of document image data 24.

Embedding patterns 14 shown in FIGS. 4A and 4B each shows a binarizedpattern of 16×16 elements two-dimensionally arranged (hereinafter,referred to as data cell). In embedding pattern 14 according to thepresent preferred embodiment, an element, which is a positionrepresenting dot D1 showing a reference position, is placed at anupper-left end in a two-dimensional space (plane). The referenceposition is a position used as the reference for judging a position of adata representing dot D3, which will be described later, in the sametwo-dimensional space. A plurality of data cells as unit patterns areembedded adjacent to one another in the image of document image data 24,so that position representing dots D1 are placed for every 16 elementsin two directions, which are an upper-lower direction (verticaldirection) and a right-left direction (horizontal direction), in theimage of composite image data 27. Position representation assisting dotsD2 are placed at positions distant from position representing dots D1 byeight elements to right and left in the same two-dimensional space. Asdescribed earlier, the same data cells are repeatedly placed adjacent toone another on the same plane (two-dimensional space), so that positionrepresentation assisting dots D2 are placed at positions distant fromposition representing dots D1 by eight elements in the upper-lowerdirection (vertical direction) and the right-left direction (horizontaldirection). Further, data representing dot D3 is placed at differentpositions in data 0 (see FIG. 4A) and data 1 (see FIG. 4B) in order toembed the information. Assuming that the information is embedded at theresolution of 600 dpi, the data cell has a side having the length of16/600 inch (0.068 cm), which is very small, and a print-out result isapparently grey as shown in FIG. 3.

An example of the arrangement of the data cells with respect to theimage of document image data 24 is shown in FIG. 5. FIG. 5 shows anexample of the arrangement of embedding patterns 14 (data cells) in thecase where embedding data 25 of four bits is embedded in four partialimage regions (i=1, 2, 3, 4) of document image data 24 having 32×32elements (all white elements). FIG. 6 shows a state where the dots areembedded in accordance with the arrangement shown in FIG. 5. In thedrawing, the image of document image data 24 has a rectangular shape anddivided into a plurality of rectangular partial regions each having thesame size as that of the data cell shown in FIG. 5. Image compositingportion 20 adjacently embeds embedding patterns 14 each corresponding tothe bit value (0 or 1) of the bit sequence of embedding data 25,starting with a leading position thereof, in accordance with apredetermined order (order from upper-left end to lower-right end of therectangular region of the image shown in FIG. 5) in the respectivepartial regions. It is assumed that the predetermined order follows anumerical order shown by a variable i in FIG. 5, and is previously setin processing steps (in the program) of image compositing portion 20.The predetermined order may follow other order.

The embedding recited in this specification refers to replacement of thevalue of each element in the partial regions of the background with thecorresponding element value of embedding pattern 14. Therefore, theelement value is updated to 1 in the case where the correspondingelement of embedding pattern 14 is black (1: dot is present), while theelement value is not updated in the case where the corresponding elementis white (0: no dot).

Referring to FIG. 7, the processing steps of image compositing portion20 according to the present preferred embodiment is described.

In image compositing portion 20, first, temporary variable i for thecontrol operation is initialized to 1 (Step S3 (hereinafter, simplyabbreviated to S)). Next, the background image of document image data 24is divided in a predetermined M number of partial image regions (S5).

Next, embedding pattern 14 corresponding to a value of ith bit (data 0or data 1) of embedding data 25 (bit sequence of coded data) is read(S7), and read embedding pattern 14 is embedded in the background imageof the ith partial region (S9). Thereafter, it is determined whether ornot a value of variable i exceeds a value of a variable M (S11). Whenthe value of variable i exceeds the value of variable M, the processingis terminated (YES in S11). When the value of variable i does not exceedthe value of variable M (NO in S11), the value of variable i isincremented by 1 (S13), and the processing returns to S7. Thereafter, S7and S9 are repeated until the value of variable i exceeds the value ofvariable M, in other words, until embedding pattern 14 of the data valueof the corresponding bit of the embedding data 25 is embedded inaccordance with the predetermine order in all of the images of the Mnumber of partial regions in the background image of document image data24.

Position representation assisting dot D2 serves to assist the display ofthe reference position by position representing dot D1. The role ofposition representation assisting dot D2 is more specifically describedin comparison to an example of the embedding pattern where positionrepresentation assisting dot D2 is not included.

In contrast to FIG. 5, when the data cell of data 0 (positionrepresentation assisting dot D2 not included) is embedded in all of thepartial regions as shown in FIG. 8, the dots are embedded as shown inFIG. 9. Observing the embedded dots in printed document 22 obtained byprinting FIG. 9, position representing dots D1 and data representingdots D3 are both placed distant by 16 elements in both of theupper-lower (vertical) direction and right-left (horizontal) directionlikewise, which makes it not possible to distinguish positionrepresenting dot D1 and data representing dot D3 from each other.

In contrast to that, when the data cell including positionrepresentation assisting dot D2 is embedded, the dots are placed in theimage of printed document 22 (image of composite image data 27) as shownin FIG. 10 even though the data cell of data 0 is embedded in all of thepartial regions as shown in FIG. 8. Therefore, in FIG. 10, anarrangement pattern of the dots shown in FIG. 11 can be detected, and acentral dot of the detected pattern can be detected as positionrepresenting dot D1. As a result, it can be determined that data 0 isembedded in the presence of the black element (dot) at the position ofdata representing dot D3 of data 0, and data 1 is embedded in thepresence of the black element (dot) at the position of data representingdot D3 of data 1 based on the detected position representing dot D1 asthe reference.

Thus, embedding pattern 14 includes, not only position representing dotD1 for representing the reference position for determining the positionof data representing dot D3 which represents the data to be embedded,but also position representation assisting dot D2 for assisting theposition representation thereof. Therefore, the position of datarepresenting dot D3 can be accurately detected.

Preferred Embodiment 2

In the preferred embodiment 1, only embedding information 12 is embeddedin the background of the image of document image data 24. In a preferredembodiment 2 of the present invention, additional information 13irrelevant to embedding information 12 is appended in addition toembedding information 12 as additional pattern 15 which is thecorresponding dot pattern. As a result, a gradation based on a dotdensity (aggregate state) of the dot pattern such as pattern or designcan be presented. However, the dot pattern of additional pattern 15 andthe dot pattern of embedding pattern 14 are different from each other.

Referring to FIG. 1, background adding portion 23 inputs additionalinformation 13 to inputted composite image data 27 (see FIG. 3) as theinformation to be added to the background of the document image thereof,that is the information to be composited into the background. Then, whenthe dot pattern (additional pattern 15) corresponding to the value ofeach element of the image data shown by inputted additional information13 is added to the background of the image of composite image data 27,composite image data 28 including the background is formed. Whencomposite image data 28 including the background is printed by outputprocessing portion 21, printed document 22 as shown in FIG. 13 isoutputted. FIG. 13 shows an example where additional information 13shown in FIG. 12 such as pattern is added to the background of theimage.

In the process implemented by background adding portion 23, additionalpatterns 15 (dot patterns) having different density values 0, 1, 2 and 3are used as additional pattern 15 as shown in FIG. 12. Additionalpattern 15 denotes information for making the background appear to be,not the grey background, but a pattern, an image or the like and isirrelevant to embedding pattern 14 used in the processing steps of imagecompositing portion 20 according to the preferred embodiment 1. It isassumed that additional patterns 15 as the dot patterns having thedensities corresponding to the density values are previously determined,for example, as shown in FIGS. 14A-14D. When these additional patterns15 are embedded, the different densities can be presented in thebackground image because the number of the dots embedded in thebackground is different depending on the density values. Each elementvalue of the image data shown by additional information 13 is any of 0,1, 2 and 3.

FIG. 15 shows an example of the arrangement of additional patterns 15(dot patterns) with respect to the image of composite image data 27.FIG. 15 is an enlarged view of a part of FIG. 12, wherein thearrangement example of additional patterns 15 added to four partialimage regions (i=1, 2, 3 and 4) in the background of the document imageof composite image data 27 having 32×32 elements (all white elements) inaccordance with additional information 13 is shown. FIG. 16 shows astate where the dots are embedded in accordance with the arrangementshown in FIG. 15. In the drawing, the image of composite image data 27is rectangular, and the background of the image is divided into aplurality of rectangular partial regions having the same size as that ofthe dot pattern (16 elements×16 elements) of additional pattern 15 asshown in FIG. 15. To the respective partial regions, additional pattern15 corresponding to the element value of the image data shown byadditional information 13 is added in accordance with a predeterminedorder (order from upper left end of the rectangular region of the imagetoward lower right end thereof in FIG. 15). The predetermined orderfollows a numeral order denoted by i shown in FIG. 15, and may followother order.

In the case of adding the density information as shown in FIG. 15 isadded to FIG. 6 as the actual arrangement example, the dots are added asshown in FIG. 16. As a result, the background of the image of printeddocument 22 additionally includes a pattern as shown in FIG. 13, and thebackground apparently including a design irrelevant to embedded data(embedding information 12) is printed. As a result, the data achieves ahigh confidentiality, and the user hardly notices that embeddinginformation 12 is embedded when he/she observes printed document 22.Therefore, the data (embedding information 12) can be embedded as adesign for a certificate or a ticket, which effectively achieves a highdata confidentiality.

Referring to FIG. 17, processing steps of background adding portion 23according to the preferred embodiment 2 are described. The image datashown by additional information 13 is a two-dimensional (planar) imagedata defined by X axis and Y axis orthogonal to each other, and atemporary variable X (X=1, 2, 3, . . . , M) for indicating the elementin a direction in parallel with the X axis and a temporary variable Y(X=1, 2, 3, . . . , N) for indicating the element in a direction inparallel with the Y axis are used. Therefore, each element is indicatedby variables (X, Y) of coordinates. It is assumed that the image datashown by additional information 13 has M number of elements in thedirection in accordance with the X axis and N number of elements in thedirection in accordance with the Y axis.

In background adding portion 23, first, temporary variables X and Y forthe control operation are initialized (Steps S15 and S16). Next, thevalue (density value) of the element (X, Y) of the image data shown byadditional information 13 is read, and additional pattern 15corresponding to the read value is read (S17 and S18). Then, readadditional pattern 15 is added to the background of composite image data27 (S19). The additional pattern 15 is added in accordance with theorder of 1, 2, 3 and 4 denoted by variable i as shown in FIG. 15.Thereafter, it is determined whether or not the value of variable Xexceeds the value of variable M (S20). When the value of variable X doesnot exceed the value of variable M (NO in S20), the value of variable Xis incremented by 1 (S21), and the processing returns to S17 so thatsteps thereafter are repeated. When the value of variable X exceeds thevalue of variable M (YES in S20), it is determined whether or not thevalue of variable Y exceeds the value of a variable N (S22). When thevalue of variable Y does not exceed the value of variable N (NO in S22),the value of variable Y is incremented by 1 (S23), and the processingreturns to S16 so that steps thereafter are repeated. When the value ofvariable Y exceeds the value of variable N (YES in S22), the processingis terminated.

Thus, additional pattern 15 corresponding to each element value of theimage data shown by additional information 13 is added to the backgroundof composite image data 27 in accordance with the order of the valuesindicated by variable i in FIG. 15 in S17-S19.

Though the four gradation degrees of 0-3 were shown as the density, thebackground appears as if a photograph can be printed when the number ofthe gradation degrees is increased to approximately eight or 16 byfurther adding the dots or the like, in other words, when the types ofadditional pattern 15 are increased. The number of the applied gradationdegrees may be arbitrarily changeable or may be set as a fixed value.

Another Example of Pattern Addition to Background

Instead of using the pattern for each density as shown in FIGS. 14A-14Dby background adding portion 23, a threshold pattern 16 shown in FIG. 18by background adding portion 231 may be used. Threshold pattern 16denotes a threshold information on whether or not the dot is turned onas in the case of a dithering process. In the foregoing manner, suchadvantages that only one pattern, which is threshold pattern 16, can beused (memory capacity can be small), a method employed in the ditheringprocess can be directly used in order to increase the number of thegradation degrees, and the like, can be enjoyed. When threshold pattern16 is utilized, the image data shown by additional information 13 isused for indicating the order of the plural partial regions of thebackground image of composite image data 27 to which the pattern inaccordance with threshold pattern 16 is added. The order indicates anorder in accordance with FIG. 15.

Threshold pattern 16 shown in FIG. 18 is a two-dimensional elementmatrix data having the same size as that of the image of each partialregion of the background of composite image data 27 (16 elements×16elements), and the value of each element (threshold value) is previouslyset to be any of 0, 1, 2 and 3 in accordance with the pattern to beadded. Background adding portion 231 executes such a processing that therelevant element value is turned on (set to 1) when the element value iscompared to the value of the corresponding element value of thresholdpattern 16 per element in each of the partial regions in the backgroundof the image of composite image data 27 and detected to be at least theelement value of threshold pattern 16.

FIGS. 19 and 20 show details of the processing steps. For convenience ofthe description, it is assumed that threshold pattern 16 shown in FIG.18 has the size of 16 elements×16 elements and is a two-dimensionalregion (planar) pattern defined by X1 axis (horizontal axis) and Y1 axis(vertical axis) orthogonal to each other.

Referring to FIG. 19, first, temporary variables X and Y for the controloperation are initialized to 1 in background adding portion 231 (StepsS27 and S28). Next, the pattern is added based on threshold pattern 16to the image of the partial region in the background of composite imagedata 27 corresponding to the element (X, Y) of the image data shown byadditional information 13 (S31). Thereafter, it is determined whether ornot the value of variable X exceeds the value of variable M (S32). Whenit is determined that the value of variable X does not exceed the valueof variable M (NO in S32), the value of variable X is incremented by 1(S34), and the processing returns to S31 so that steps thereafter arerepeated. When it is determined that the value of variable X exceeds thevalue of variable M (YES in S32), it is determined whether or not thevalue of variable Y exceeds the value of variable N (S33). When it isdetermined that the value of variable Y does not exceed the value ofvariable N (NO in S33), the value of variable Y is incremented by 1(S35), and the processing returns to S28 so that steps thereafter arerepeated. When it is determined that the value of variable Y exceeds thevalue of variable N (YES in S33), the processing is terminated.

Thus, the background adding process in which threshold pattern 16 isused (S31) is repeatedly executed for each of the images of the partialregion indicated by each element of the image data shown by additionalinformation 13 in the images of the partial regions in the background ofcomposite image data 27.

Referring to FIG. 20, the process of S31 shown in FIG. 19 is described.For example, a variable X1 for counting the number of the elements ofthe partial image in the background image of composite image data 27shown in FIG. 10 and the image of threshold pattern 16 in an X1-axis(horizontal) direction and a variable Y1 for counting the number of theelements in a Y1-axis (vertical) direction are used.

First, the values of variables Y1 and X1 are initialized to 1 (S37 andS39). Then, the element of threshold pattern (hereinafter, referred toas element A) (X1, Y1) and the value of the element of the partial imageof composite image date 27 (hereinafter, referred to as element B) (X1,Y1) are compared to each other (S41). When it is determined that A (X1,Y1)≦B (X1, Y1) is established as a result of the comparison (YES inS43), the value of the element B (X1, Y1) is updated to be a valueshowing a state where the dot is included (for example, 1) (S45). Whenit is determined that the foregoing equation is not obtained (NO inS43), the value of the element B (X1, Y1) is not updated. Thereafter, itis determined whether or not the value of variable X1 is at least 16(S47). When it is determined that the value of variable X1 is not atleast 16 (NO in S47), the value of variable X1 is incremented by 1(S49). Then, the processing advances to S39 so that steps after S39 areimplemented in a similar manner.

When it is determined that the value of variable X1 is at least 16 (YESin S47), the value of variable Y1 is incremented by 1 (S51). Thereafter,it is determined whether or not the value of variable Y1 exceeds 16, inother words, whether or not the background pattern addition in whichthreshold value 16 is used has been completed with respect to all of theelements B (X1, Y1) of the image data in the partial regions. When it isdetermined that the value of variable Y1 exceeds 16 (YES in S53), thesuccessive processing is terminated. When it is determined that thevalue of variable Y1 does not exceed 16 (NO in S53), the processingreturns to S39 so that steps thereafter are implemented in a similarmanner.

The embedding process for embedding information 12 by image compositingportion 20 and the process by background adding portion 23 or backgroundadding portion 231 may not be necessarily implemented in the order ofFIG. 1. The process by image compositing portion 20 may be implementedafter the process by background adding portion 23 (or background addingportion 231).

Preferred Embodiment 3

A preferred embodiment 3 of the present invention recites a functionadded to the preferred embodiment 2. More specifically, in the case ofusing additional pattern 15 or threshold value 16 for adding additionalinformation 13 irrelevant to embedding information 12 is added,additional information 13 is added in such a manner that makes itdifficult to read a copying result obtained by copying outputted printeddocument 22 (paper) in a copying machine.

Only the points which differentiate the preferred embodiment 3 from thepreferred embodiment 2 are described. It is assumed that each elementvalue of the image data shown by additional information 13 has any ofdensity values 0, 1, 2, 3, 4 and 5. Further, it is assumed that theplural additional patterns 15 show the respective dot patternscorresponding to the six density levels 0-5 as shown in FIGS. 21A-21F.Observing the background of the image of printed document 22 to whichadditional patterns 15 are thus added by background adding portion 23,the density appear to gradually increase from the density 0 to thedensity 5.

However, when printed document 22 (paper) is copied in the copyingmachine, most of the independent dots printed at the printing resolutionof 600 dpi disappear in the copied image because the copying machinegenerally processes the background of the image to be presented in whiteunder the influence of a resolving power of a scanner and a basicprocess. Then, any other dot can easily remain in the copied documentimage as the number of the aggregated dots is increased such as twoaggregated dots or three aggregated dots. Therefore, in the copyingresult of additional patterns 15 having the density 3 in FIG. 21D andthe density 4 in FIG. 21E, the densities are reversed. Further, thedensity 2 in FIG. 21C and the density 5 in FIG. 21F appear to be at thesame level of density. Therefore, as the state where the dots areaggregated (state where the dots are arranged) in additional pattern 15is changed in accordance with the density, the background of the copiedimage is apparently different from the background of the image ofcomposite image data 28 including the background as original printeddocument 22. Therefore, in the case of any identification or the likewhose illegal copy is desirably prevented, for example, the copieddocument and the original document can be easily discriminated from eachother.

Further, such a dot pattern (additional pattern 15) that makes the imageof printed document 22 appear to have the same density but appear to bedifferent in the image of the copied printed document 22 can be used sothat the original document and the copied document can be easilydiscriminated from each other. It becomes difficult to read originaldocument data 11 since the copied document has the dot pattern differentfrom that of printed document 22.

Preferred Embodiment 4

A preferred embodiment 4 of the present invention recites anotherexample of data representing dot D3 in embedding pattern 14 according tothe preferred embodiment 1. Below is given a description on differencesbetween the preferred embodiments 1 and 4.

In image compositing portion 20, which embeds embedding pattern 14 ofdata 0 or data 1 in accordance with the bit sequence of embedding data25 in the background of the image of document image data 24, differentpositions shown in FIGS. 22A and 22B may be used as the position of datarepresenting dot D3 of embedding pattern 14 in place of the positionsshown in FIGS. 4A and 4B. In this case, data representing dot D3 of data1 in FIG. 22B is at the same position as the dot used for representingthe density in FIG. 14B in the preferred embodiment 2. The datarepresenting dot according to the present invention is not limitedlyplaced at a specific position.

In FIGS. 4A and 4B, or FIGS. 22A and 22B, embedding data 25 is convertedinto the two-value code which represents data 0 and data 1. As shown inFIGS. 23A-23D, embedding information 12 can be embedded as dataconverted into a four-value code representing 0, 1, 2 and 3. Accordingto such an embedding method, an amount of embedding information to beembedded 12 can be increased. The positions of position representing dotD1 and position representation assisting dot D2 in FIGS. 23B-23D are thesame as those shown in FIG. 23A.

Preferred Embodiment 5

Another example of position representation assisting dot D2 isdescribed. In a preferred embodiment 5 of the present invention,differences with respect to the preferred embodiment 1 are described.

As the position of position representation assisting dot D2 in embeddingpattern 14 used in the process for embedding the data sequence inaccordance with the bit sequence of embedding data 25 by imagecompositing portion 20, positions shown in FIGS. 24A and 24B may be usedin place of those shown in FIGS. 4A and 4B. When a pattern shown in FIG.25 is used in the image of printed document 22 in place of the patternof FIG. 11, the dot arrangement in the image corresponding to thepattern is detected so that it can be determined that positionrepresenting dot D1 is placed at the element in the center of thedetected pattern. Therefore, it can be determined if the data embeddedas the detected pattern is data 0 or data 1 in a manner similar to FIG.11.

Further, one position representation assisting dot D2 as shown in FIGS.26A and 26B may be used in place of two position representationassisting dots D2 shown in FIGS. 4A and 4B. When a pattern shown in FIG.27 is used in place of the pattern of FIG. 11, the dot arrangement inthe image corresponding to the pattern is detected so that it can bedetermined that position representing dot D1 is placed at a left-sideelement in the detected pattern. Therefore, it can be determined if thedata embedded as the detected pattern is data 0 or data 1 in a mannersimilar to FIG. 11.

As described, the position representation assisting dot is not limitedlyplaced at a specific position in the present invention.

Preferred Embodiment 6

In a preferred embodiment 6 of the present invention, a plurality ofembedding patterns 14A (dot patterns) for representing embeddinginformation 12 and additional information 13 are prepared and used fordifferent purposes so that the information is embedded.

In the preferred embodiment 6, the process for embedding the informationin the image of document image data 24 has only one step by an imagecompositing portion 201 as shown in FIG. 28. Image compositing portion201 inputs embedding data 25 and read additional information 13 (imagedata) to the background of the image of inputted document image data 24.When embedding patterns 14A are embedded in accordance with the datasequence (see FIG. 12), a composite image data 27A similar to the datashown in FIG. 13 can be obtained. FIGS. 29A-29H show embedding patterns14A according to the preferred embodiment 6. The embedding pattern 14Aincludes data representing dot D3 and an additional dot D4 forrepresenting the density of the background image. FIG. 30 showsprocessing steps of image compositing portion 201. The processing stepsare different from those shown in FIG. 17 in that S18 and S19 in FIG. 17are replaced with S18 a and S19 a with any other step remaining the sameas in FIG. 17.

In S18 a, embedding data forming portion 18 converts embeddinginformation 12 into a two-value code and outputs converted embeddingdata 25 to image compositing portion 201. Image compositing portion 201further reads additional information 13. Image compositing portion 201reads any of embedding patterns 14A determined based on combinations ofthe value of each bit of the bit sequence (0 or 1) and the density valueof each element (any of 0, 1, 2 and 3) of the image data, that areembedding patterns 14A of eight different types shown in FIGS. 29A-29H,based on inputted embedding data 25 of the bit sequence and the imagedata shown by read additional information 13. In S19 a, read embeddingpatterns 14A are sequentially embedded in the images of the pluralpartial regions of the background image of document image data 24 whilethe values of variables X and Y are incremented by 1 (S21 and S23). Theembedding patterns 14 are embedded, for example, in the order of theregion denoted by the value of variable i in FIG. 15 (1, 2, 3 and 4).

In the case of embedding the data and the density information as shownin FIG. 31, the dots are embedded in the image as shown in FIG. 32according to image compositing portion 201. In the embedding, the dotpattern of the data value can be defined for each density value, and theposition of additional dot D4 can be thereby changed based on embeddinginformation 12. Therefore, it is advantageous in that the printed imageof printed document 22 can have a pattern where the dots areappropriately dispersed because additional dots D4 can be embedded notintensively but dispersedly.

Preferred Embodiment 7

Next, an apparatus for extracting position representing dot D1 and datarepresenting dot D3 from the image of outputted printed document 22(paper) according to the preferred embodiments 1 and 2 by means of thefiltering processing and detecting embedding information 12 based on aresult of the extraction is described. It is assumed that theinformation detecting apparatus is previously supplied with informationrelating to details of embedding pattern 14 applied at the time ofembedding the information.

FIG. 33 shows functional components for detecting embedding information12. Referring to FIG. 33, an embedding information detecting apparatus50 reads printed document 22 as a printing result of the image in whichembedding information 12 is embedded from an input portion 30 andoutputs an image data 32. Input portion 30 outputs a multi-value imagedata 32 through a reading operation. Multi-value image data 32 is shownas a grey image of 256 gradation degrees. Multi-value image data 32 issupplied to a position representing dot extracting portion 33 and a datarepresenting dot extracting portion 34.

Position representing dot extracting portion 33 processes multi-valueimage data 32 using a position filter 38 previously prepared, extractsposition representing dot D1 in embedding pattern 14, and supplies aposition representing information 381 showing a result of the extractionto an embedding data detecting portion 35. Data representing dotextracting portion 34 processes multi-value image data 32 using a datafilter 39 previously prepared, extracts data representing dot D3, andsupplies a data representing information 391 showing a result of theextraction to embedding data detecting portion 35.

Position filter 38 functions to extract position representing dot D1,and data filter 39 functions to extract data representing dot D3.

Embedding data detecting portion 35 detects embedding data 25 usingsupplied position representing information 381 and data representinginformation 391, and supplies detected embedding data 25 to an embeddinginformation detecting portion 36.

Embedding information detecting portion 36 forms embedding information12 based on supplied embedding data 25, and supplies formed embeddinginformation 12 to an output portion 37. Output portion 37 outputssupplied embedding information 12 outside (to an external apparatus notshown via display portion 71 or communication I/F 74 and communicationlines 75). These portions are previously stored as programs in memory62, HDD 63, FD 65, DVD 67 and the like and read and executed by MPU 61so that the functions of the respective portions are realized. Further,position filter 38 and data filter 39 are previously stored in memory62, HDD 63, FD 65, DVD 67 and the like.

Below is given a detailed description. First, it is assumed that inputportion 30 controls scanner 70 to thereby read printed document 22 onpaper, and outputs multi-value image data 32 as shown in FIG. 16. It isassumed that white elements indicate the value of 255, and blackelements indicate the value of 0. When all of the elements ofmulti-level image data 32 are subjected to such a filtering processingthat an element value of multi-value image data 32 corresponding to ablack element in FIG. 34 is replaced with a maximum value of fiveelement values of position filter 38 having five elements of black orgrey (shadowed areas) (others are white elements) in FIG. 34, a resultshown in FIG. 35 is obtained.

Position Representing Dot Extracting Portion

Actual multi-value image data 32 is as shown in FIG. 36. When positionrepresenting dot extracting portion 33 executes the filtering processingusing position filter 38 shown in FIG. 34, a result shown in FIG. 37(position representing information 381) is obtained. The filteringprocessing serves as such a pattern matching process that the value ofthe element (X, Y) corresponding to the black element having the dotarrangement shown in FIG. 34 is extracted as a blackish value inmulti-value image data 32.

As the conventional pattern matching process, a so-called simplesimilarity processing, for example, is adopted. As a determining methodbased on the simple similarity is available a method in which such adetermination is made that as an angle made by two vectors, which are areference pattern c=(c1, c2, . . . , c289) and an input pattern x=(x1,x2, . . . , x289), is smaller, the both patterns are more similar toeach other. Position filter 38 shown in FIG. 34 corresponds to thereference pattern c. In the determining method, c·x/(|c|×|x|) is to beobtained. · denotes an inner product of the vector, and | | denotes asize of the vector. Then, cos θ is calculated regarding an angle θ madeby the two vectors shown in the foregoing expression, and it isdetermined that the both vectors are similar to each other as a value ofthe cos θ is closer to 1.

In comparison to the determining method, a method according to thepreferred embodiment 7 can attain a very high processing speed becausethe number of the elements used for the matching is such a small numberas five as shown in FIG. 34. On the contrary, 289 elements are used, inother words, all of the elements are used for the comparison, in thesimple similarity processing, which fails to achieve a high speed.Further, the simple similarity is reduced in the case of includingadditional dot D4 added for representing the density and noise componentsuch as smear in printing, while the method according to the presentpreferred embodiment is only slightly affected by the foregoing factorsas shown in FIG. 37.

Data Representing Dot Extracting Portion

Next, the processing for extracting data representing dot D3 by datarepresenting dot extracting portion 34 is recited below. When afiltering processing for replacing the value of the black element (X, Y)of the image shown in FIG. 16 corresponding to a black element shown inFIG. 38 with a maximum value of five elements values of data filter 39having black or grey (shadowed parts) five elements (others are whiteelements) shown in FIG. 38, is executed to all of the elements of theimage of FIG. 16, a result shown in FIG. 39 (data position information391) is obtained.

Because the image of multi-value data 32 is as shown in FIG. 36, aresult shown in FIG. 40 is outputted when data filter 39 of FIG. 38 isused to execute the filtering processing. The filtering processingrefers to such a processing as a pattern matching processing forextracting the dots arranged as shown in data filter 39 of FIG. 38 inthe blackish color.

Of a plurality of position filters 38 and data filters 39 which areprepared, a filter capable of extracting position representing dot D1and data representing dot D3 of embedding pattern 14 applied to printeddocument 22 is designated for the reading operation. The filter isdesignated based on the user's operation via keyboard 68.

Embedding Data Detecting Portion

Embedding data detecting portion 35 processes the results of the twodifferent filtering processes (position representing information 381 anddata position information 391) referring to embedding pattern 14 tothereby extract the data embedded in the image of printed document 22.More specifically, any (blackish) element at most a certain thresholdvalue in FIG. 37 (position representing information 381) is determinedas position representing dot D1 when the data is embedded. When it isdetermined that the element at a position advanced to right by 12elements from the element thus determined referring to embedding pattern14 indicates the (blackish) element at most the certain threshold valuein FIG. 40 (data position information 391) (because the dots areembedded as shown in FIGS. 4A and 4B), it is detected that data 0 isembedded. Alternatively, when it is determined that an element at aposition advanced to right by four elements referring to embeddingpattern 14 indicates the (blackish) element at most the certainthreshold value in FIG. 40 (because the dots are embedded as shown inFIGS. 4A and 4B), it is detected that data 1 (refer to embedding pattern14 in FIG. 4A) is embedded. When the foregoing processing iscontinuously executed, the embedded data can be extracted.

In the data detecting processing, the original image shown in FIG. 36can be used in place of FIG. 40, which increases the processing speed.However, a noise resistance is low in comparison to the use of datafilter 39 in FIG. 40 because a number of unnecessary dots are placed inFIG. 36. As a result, the detecting accuracy is not satisfactory.

Referring to FIGS. 41-43, processing steps of the extractions of theposition representing dot and data representing dot are described. Theprocessing steps shown in FIG. 41 are applied to both of the extractionsof the position representing dot and data representing dot.

First, positions of variables X and Y for identifying each element ofthe image of multi-value image data 32 are set and the variables areinitialized (S61 and S63). Variable X for counting the number of theelements in the X (horizontal) direction in the two-dimensional regionof the image of multi-value image data 32 and variable Y for countingthe number of the elements in the Y (vertical) direction in the samemanner are used.

Thereafter, the post-filtering value is outputted to the element (X, Y)of the image of multi-value image data 32 (S65). This processing will bedescribed later.

Variable X is incremented by 1 (S67). Then, it is determined whether ornot the value of variable X exceeds a predetermined value M as a resultof the increment (S69). More specifically, it is determined in thedetermining process whether or not the processing of S65 was executed toall of the elements in the X direction in the two-dimensional image ofmulti-level image data 32. When it is determined that the processing wasnot executed to all of the elements (NO in S69), the processing returnsto S65 so that the same processing is executed to the next element. Whenit is determined that the value of variable X exceeds the predeterminedvalue M, (YES in S69), the value of variable Y is incremented by 1(S71), and the same processing is repeatedly executed to the elements inthe next sequence. Thereafter, it is determined whether or not the valueof incremented variable Y exceeds the value of variable N, that is,whether or not the processing (S65) was executed to all of the elementsin sequence in the vertical direction of the image of multi-value imagedata 32. When it is determined that the processing was executed to allof the elements (YES in S73), the successive processing is terminated.When it is determined that the processing was not executed to all of theelements (NO in S73), the processing returns to S63, in which variable Xis initialized to 1 so that the processing (S65) is executed. Then, thesame processing is repeatedly executed to the elements in the nextsequence likewise.

Thus, the filtering processing (S65) is executed to all of the elementsof the image of multi-value image data 32 while variables X and Y arethus incremented by 1. This processing includes the processing ofposition representing dot extracting portion 33 and the processing ofdata representing dot extracting portion 34.

Next, processing steps of position representing dot extracting portion33 in the replacement (S65) of the value of the element (X, Y) ofmulti-value image data 32 are described referring to FIG. 42.

In accordance with the dot arrangement of position filter 38, an element(X, Y) value is assigned to a variable A1, an element (X+8, Y) value isassigned to a variable A2, an element (X−8, Y) value is assigned to avariable A3, an element (X, Y+8) value is assigned to a variable A4, andthe value of element (X, Y−8) is assigned to a variable A5 (S81-S89). Asa result, a maximum value of variables A1-A5 is outputted as apost-processing value with respect to the element (X, Y) (S91). Whenthere is no element at a relevant position in S81-S89, 0 is set as thevariables.

Next, processing steps of data representing dot extracting portion 34are described referring to FIG. 43. In accordance with the dotarrangement of data filter 39, the element (X, Y) value is assigned tovariable A1, an element (X+4, Y) value is assigned to variable A2, anelement (X+12, Y) value is assigned to variable A3, an element (X−4, Y)value is assigned to variable A4, and an element (X−12, Y) value isassigned to variable A5 (S101-S109). As a result, a maximum value ofvariables A1-A5 is outputted as a post-processing value with respect tothe element (X, Y) (S110). When there is no element at a relevantposition in S101-S109, 0 is set as the variables.

Thus, the filter which reacts with the embedded dot is used for thefiltering processing based on the embedded dot pattern (embeddingpattern 14) in information detecting apparatus 50, the detection of thenoise (unnecessary dot unintentionally printed and dot resulting fromthe screening process) by mistake can be prevented with a higherpossibility. Further, only the information to be extracted (informationof embedding pattern 14) can be detected even after any unnecessary dot(dot in accordance with additional data 15) is placed. As a result, adegree of freedom in designing of the background can increased while thedetecting accuracy is maintained.

Preferred Embodiment 8

According to a preferred embodiment 8 of the present invention, anotherexample of the filtering processing is recited. In the case whereposition representing dot D1 and position representation assisting dotD2 are placed as shown in FIGS. 24 (A) and (B) and printed, and positionrepresenting dot D1 is extracted from the image of multi-value imagedata 32 obtained by scanning the printed image, a filtering process foroutputting a maximum value of five elements of black and grey (shadowedparts) of a filter shown in FIG. 44 as a value with respect to the blackelement for each element of the image of multi-value image data 32 isexecuted. Thus, position representing dot D1 can be extracted in amanner similar to the preferred embodiment 7.

In the case where position representing dot D1 and positionrepresentation assisting dot D2 are placed as shown in FIGS. 26 A and Band printed, and position representing dot D1 is extracted from theimage of multi-value image data 32 obtained by scanning the printedimage, a filtering process for outputting a maximum value of twoelements of black and grey (shadowed parts) of a filter shown in FIG. 45is outputted as a value with respect to the black element is executed.Alternatively, a filtering process for outputting a maximum value offive elements of black and grey (shadowed parts) of a filter shown inFIG. 46 is outputted as a value with respect to the black element may beexecuted.

In the case of extracting the element via the different filters appliedfor the extraction, results thereby obtained are different as follows.Below is given an example where an unnecessary dot is printed at such anelement position as the noise in the image of printed document 22 asshown in FIG. 47 provided that the dots other than the noise element arerepeatedly printed horizontally and vertically. When the filter of FIG.45 is applied to the image of multi-value image data 32, an element at awrong position by one element is extracted due to the noise element asshown in FIG. 48. When the filter of FIG. 46 applied, the element can beextracted without any wrong element as shown in FIG. 49 irrespective ofthe noise.

More specifically, in the filtering process, the dots at the position ofthe element desirably extracted and at the same repeated positions(repeated positions for every 16 elements) are utilized to output theelement desirably extracted. It can be learnt that the filteringprocessing is enhanced against the noise when the number of the elementsused in the filtering processing is increased to a certain degree.

Further, in the case of extracting data representing dot D3 from theimage of multi-value image data 32 obtained by scanning printed document22 in which data representing dot D3 is placed as shown in FIGS. 22 Aand B, a filter including the elements of black and grey (shadowedparts) shown in FIG. 50 is applied to extract data 0, and a filter ofFIG. 51 is applied to extract data 1. Then, the respective datarepresenting dots D3 can be extracted.

Preferred Embodiment 9

A preferred embodiment 9 of the present invention recites a filteringprocessing in the case where the image of multi-value image data 32obtained by reading the image of printed document 22 by scanner 70 istitled. Assuming that scanned multi-value image data 32 is tilted asshown in FIG. 52, a tilting angle indicating a tilting degree in thecase where two large dots (dots apparently larger than the dots embeddedin the background of the document image) are printed and a straight lineconnecting the two dots is compared to a reference straight line(straight line connecting two dots in multi-value image data 32 which isnot tilted) can be detected as in a conventional method. Therefore, aposition filter 38 tilted in accordance with the detected tilting angleshown in FIG. 53 can be applied in place of position filter 38 shown inFIG. 34. As a result of the application of the filter, the image(position representing information 381) shown in FIG. 54 can be obtainedby position representing dot extracting portion 33.

Preferred Embodiment 10

A preferred embodiment 10 of the present invention recites still anotherexample of the filtering processing for the two-value image. It isassumed that in the present preferred embodiment, in the case ofextracting data representing dot D3 from the image of multi-value imagedata 32 obtained by scanning printed document 22 in which datarepresenting dot D3 is placed as shown in FIG. 22B using scanner 70, itis determined whether or not the value of each element of the image ofmulti-value image data 32 exceeds a particular threshold value, and thevalue is binarized so that value 1 denoting the presence of the dot isshown when the value exceeds the threshold value and value 0 denotingthe absence of the dot is shown when the value does not exceed thethreshold value.

The filter of FIG. 50 is applied for extracting data 0, while the filterof FIG. 51 is applied for extracting data 1, in which case the elementvalue is larger as the density of the element is higher (darker).Therefore, a minimum value is outputted in place of the output of themaximum value as the value of the element (X, Y) as in the preferredembodiments described so far.

Further, the processing for outputting the minimum value itself may beadapted to output an AND value of the values (0 or 1) of the fourelements (dots) shown in FIGS. 50 and 51. The same result is therebyobtained, and the processing speed can be increased because only one ANDcalculation is adopted in place of search of the minimum value.

Preferred Embodiment 11

A preferred embodiment 11 of the present invention recites still anotherexample of the filtering processing for the two-value image. It isassumed that FIG. 56 shows the image of multi-value image data 32obtained by scanning and binarizing printed document 22 in which thedata is embedded according to the data representation shown in FIGS. 22Aand 22B as shown in FIG. 55. In the present preferred embodiment,filters shown in FIGS. 57 and 58 are applied in place of the filters ofFIGS. 50 and 51 recited in the preferred embodiment 10. these filterscalculate an inversion value of a bit value (1 or 0) of an element 384at a predetermined position surrounded by a thick square and an ANDvalue using bit values (1 or 0) of other five elements of grey or black(shadowed parts) and output the calculated values to the element (X, Y).The inversion of the bit value of element 384 means that such acondition that there is no dot in the element at the predeterminedposition indicated by element 384 is added to the filtering processing.

An effect obtained by applying the filters of FIGS. 57 and 58 isdescribed in comparison to the preferred embodiment 10. In the casewhere one element is added as the noise as shown in FIG. 56, thefiltering processing according to the preferred embodiment 10 results inFIGS. 59 and 60, and a wrong dot is extracted in FIG. 60. On the otherhand, when the filters according to the preferred embodiment 11 shown inFIGS. 57 and 58 are applied, there is no wrong dot extracted as shown inFIGS. 61 and 62, which shows that the obtained noise resistance ispreferably improved. More specifically, when multi-value image data 32as the two-value image is processed, the filtering processing includingthe absence of the dot as the additional condition is executed so thatthe noise resistance preferably improved can be obtained by thefiltering processing.

Preferred Embodiment 12

FIG. 63 shows a schematic configuration of a personal computer (PC) inwhich the information embedding apparatuses and the informationdetecting apparatuses according to the preferred embodiments describedso far are installed. A monitor 81 corresponding to display portion 71,a mouse 82, keyboard 68, HOD 63, an external memory portion 84corresponding to FD 65 and DVD 67, and scanner 70 are connected to a PC80. An image processing software as a program for instructing theprocessing steps according to the preferred embodiments for embedding ordetecting the information is stored in memory 62 in PC 80. The softwareis read and executed by a CPU (Central Processing Unit) not shown or MPU61 in PC 80.

FIG. 64 shows a schematic configuration of the MFP in which theinformation embedding apparatuses and the information detectingapparatuses according to the preferred embodiments are installed. Ascanner unit 91 including scanner 70, an operation panel unit 92including keyboard 68 and a printer unit 93 including printer 73 areconnected to a MFP main body 90. The MFP main body 90 includes an imageprocessing H/W94 for realizing hardware-wise (H/W) the processing stepsfor embedding the information or the processing steps for detecting theinformation according to the preferred embodiments. Image processingH/W94 includes an ASIC (Application Specific Integrated Circuit).

FIG. 65 shows a data input/output relationship regarding PC 80 shown inFIG. 63. PC 80 includes an input/output interface 85 for controllinginput/output between MPU 61 and outside (keyboard 68, mouse 82, monitor81, scanner 70 and external memory portion 84). The user operateskeyboard 68 and mouse 82 to thereby input his/her instruction thereto.Monitor 81 displays the various informations such as the supplied imagedata. Scanner 70 scans printed document 22 based on the instruction andoutputs the scanned image data corresponding to multi-value image data32. MPU 61 includes an OS (Operating System) 87 and a processingoperating portion 86 controlled by OS 87. The program is read frommemory 62 while the data is inputted/outputted with outside viainput/output interface 85 and executed in processing operating portion86. An execution state of the program is controlled and monitored by OS87.

Although the present invention has been described and illustrated indetail, it is clearly understood that the same is by way of illustrationand example only and is not to be taken by way of limitation, the spiritand scope of the present invention being limited only by the terms ofthe appended claims.

1. An information detecting apparatus for detecting a predeterminedinformation in accordance with a predetermined dot pattern printed on apredetermined region of a sheet of paper comprising: a particularelement dot detecting portion for scanning said predetermined regionusing an element matrix for detecting an element corresponding to anidentifying dot used for identifying said predetermined information ofsaid predetermined dot pattern and detecting a dot of the element insaid predetermined region relevant to a particular element correspondingto said identifying dot of said element matrix; and an informationdetecting portion for detecting said predetermined information based ona result of the detection by said particular element dot detectingportion and said predetermined dot pattern; wherein said predetermineddot pattern includes a data dot placed at a position in accordance withsaid predetermined information, a position dot placed at a position forinstructing a reference position used for identifying the position ofsaid data dot, and an assisting dot placed at a position for assistingthe instruction of the reference position by said identifying dot, andsaid identifying dot indicates a dot for detecting the position of thedata dot.
 2. The information detecting apparatus according to claim 1,wherein said identifying dot indicates said data dot.
 3. The informationdetecting apparatus according to claim 1, wherein said identifying dotindicates said position dot.
 4. The information detecting apparatusaccording to claim 1, wherein said particular element dot detectingportion detects the dot of said element in said predetermined regioncorresponding to the element of the element matrix relevant to aposition where the dot is not placed in said predetermined dot pattern,and detects the dot of the element in said predetermined regioncorresponding to said particular element in said element matrix based ona result of the detection.
 5. The information detecting apparatusaccording to claim 1, wherein said predetermined dot pattern indicates aunit pattern having a plurality of predetermined elementstwo-dimensionally arranged, and said predetermined dot patterns areprinted adjacent to each other on said predetermined region of the sheetof paper.
 6. An information detecting method for detecting apredetermined information in accordance with a predetermined dot patternprinted on a predetermined region of a sheet of paper using a computercomprising the steps of: scanning said predetermined region using anelement matrix read from a memory for detecting an element correspondingto an identifying dot used for identifying said predeterminedinformation of said predetermined dot pattern and detecting a dot of anelement in said predetermined region relevant to a particular elementcorresponding to said identifying dot of said element matrix; anddetecting said predetermined information based on a result of thedetection obtained in the particular element dot detecting step and saidpredetermined dot pattern; wherein said predetermined dot patternincludes a data dot placed at a position in accordance with saidpredetermined information, a position dot placed at a position forinstructing a reference position used for identifying the position ofsaid data dot, and an assisting dot placed at a position for assistingthe instruction of said reference position by said position dot, andsaid identifying dot indicates a dot for detecting the position of saiddata dot.
 7. The information detecting method according to claim 6,wherein said predetermined dot pattern indicates a unit pattern having aplurality of predetermined elements two-dimensionally arranged, and saidpredetermined dot patterns are printed adjacent to each other on saidpredetermined region of the sheet of paper.